title: Modulation of hepatic level of microsomal testosterone 7 alpha-hydroxylase, P-450a (P450IIA), by thyroid hormone and growth hormone in rat liver.
abstract: The effects of thyroid hormone and growth hormone on microsomal testosterone 7 alpha-hydroxylase, P-450a, were studied to understand the interaction of these hormone-mediated regulations in rats. In Western blots using anti-P-450a IgG, 1.7-fold higher content of P-450a was observed in livers of female than male adult rats, while no appreciable sex-related difference was detected in prepubertal rats and rats of 24 months of age. Treatment with n-propyl-2-thiouracil or thyroidectomy of male rats increased by 2-fold the hepatic content of P-450a, but neither regimen had a significant effect on the content in female rats. Levels of P-450a in both sexes of thyroidectomized rats were decreased by the supplementation of triiodothyronine (T3, 50 micrograms per kg, i.p. for 7 days) to levels similar to that observed in normal male rats. Hypophysectomy also caused an increase in microsomal P-450a content in male rats. Continuous infusion of human growth hormone, which mimicked the female secretion, further significantly increased the content in hypophysectomized rats to a level similar to that observed in normal female rats. In contrast, hepatic level of P-450a in hypophysectomized male and female rats was reduced by intermittent injection, which mimicked the male secretion. Clear suppression on the level of hepatic P-450a was also observed by the treatment of hypophysectomized rats with 5 or 50 micrograms/kg of T3 and of hGH-infused hypophysectomized rat with 50 micrograms/kg of T3.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, School of Medicine, Keio University, Tokyo.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamazoe
authors.forename: X
authors.initials: X
authors.lastname: Ling
authors.forename: N
authors.initials: N
authors.lastname: Murayama
authors.forename: D
authors.initials: D
authors.lastname: Gong
authors.forename: K
authors.initials: K
authors.lastname: Nagata
authors.forename: R
authors.initials: R
authors.lastname: Kato
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology*; D006900:Hydroxylation; D007016:Hypophysectomy; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013965:Thyroidectomy; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D014284:Triiodothyronine; D013006:Growth Hormone; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C022724:testosterone 7-alpha-hydroxylase, hamster